Dental resins are polymeric materials that are used to construct dental structures such as restorations, prostheses and appliances. They are brittle, isomeric materials that exhibit relatively poor stress-bearing properties. In order to enhance the stress-bearing properties of dental resins and to minimize crack propagation, fiber reinforcements have been incorporated within dental resins. Fiber-reinforced dental resins are anisotropic materials that derive their strength and stiffness from reinforcing fibers embedded within the resin. The orientation of the reinforcing fibers provides directionality to the properties and performance attributes of the resin. The properties and performance attributes of fiber-reinforced dental resins include, for example, the ability of the resin to resist an externally applied shearing force.
Resins that include reinforcing fibers that are all oriented in one direction are restricted to performance in the direction of the reinforcing fibers. Thus, for example, the ability of a resin, that includes reinforcing fibers that are all oriented in one direction, to resist a shearing force applied at any angle other than along the axis of the reinforcing fibers approaches that of the unreinforced resin. Additionally, prior to curing, the resin is unstable since it can easily shear and thereby deform in a direction that is transverse to the direction of the fibers. Thus, for example, when an uncured resin, that includes reinforcing fibers that are all oriented in one direction, is being manipulated to conform to the contours of the teeth and or the dental arch, the material has a tendency to shear and deform in a direction that is transverse to the longitudinal axis of the fibers.
One attempted solution to the problem of shear and deformation of resins, that includes reinforcing fibers that are all oriented in one direction, has been to reinforce resins with biaxial weaves which are fabrics that include reinforcing fibers oriented in two, usually orthogonal, directions. Thus, biaxial weaves are able to resist shearing in two directions. Nonetheless, in a biaxial weave individual fiber bundles or yarns can still slide past each other, thereby causing the fabric to shear and deform. Further, biaxial weaves cannot resist deformation caused by an external force applied in any direction other than the two directions in which the reinforcing fibers are oriented. Deformation and shear is a problem, for example, when the fabric is impregnated with resin to form a composite, or when the fabric is manipulated to conform to the contours of a tooth or the dental arch.
Thus, there is a need for a method of constructing, reinforcing or modifying dental structures so that they are mechanically stable and can resist external forces applied from various directions.